1. Field of the Invention
The present invention generally relates to a motion image processing apparatus, a computer readable recording medium recorded with program code for causing a computer a computer to process a motion image, and a motion image processing method, that reproduce motion image data being compressed by using a digital motion image compressing method for conducting an image compressing process only for information within a frame.
2. Description of the Related Art
Generally, in a case of transmitting and accumulating digital motion image data, the digital motion image data are compressed into functional tenths by using a digital motion image compressing and decompressing technology so as to reduce a transmission rate and an accumulated amount of data. As this digital motion image compressing and decompressing technology, MPEG 1, MPEG 2, and MPEG 4 are used for a motion image only and Motion JPEG handling a still image as a sequence of successive frames is used.
The Motion still image coding method handles only a coding process within each frame. The MPEG method handles not only images within the same frame but also correlates between images among different frames, so that compression is further effectively conducted. On the other hand, the motion still image coding method, which separately handles each of the frames, can edit for each frame, which cannot be possible in the MPEG method. In addition, a transmission error occurring in one frame does not affect other frames. As described above, the MPEG method and the Motion still image coding method haves features, respectively. Either one is used approximately for each application.
Recently, for the Motion still image coding method, a new method called Motion JPEG 2000, which compresses and codes image data by using a discrete wavelet transform is standardized.
However, since many coding methods such as the MPEG method and the Motions still image coding method process an image per block unit, deterioration such as a block noise and an edge noise occurs when the image is decoded. The block noise is a distortion seen as geometric patters being a block pattern, which do not exist in an original image. And the edge noise is a distortion being a ringing shape and occurring in a vicinity of edges (called a mosquito noise).
Conventionally, a post filter has been provided to eliminate noises peculiar to these coding methods. Schematically, this post filter conducts processes for smoothing a decoding image signal, and eliminating a high component at a boundary portion between blocks.
However, a filtering process such as the above-described post filter relatively requires a large amount of operations. Since the filter process consumes a time, a reproducing process is delayed as a result. Especially, in a system conducting a software decoding process on a microprocessor basis, a processor resource is occupied by the decoding process alone for a scene of a vigorous movement and a workload of the processor is increased. Then, a delay is frequently caused in the reproducing process. The delay in the reproducing process is actualized especially when a decoding process and the reproducing process are conducted with respect to a motion image by synchronizing a voice by software. Accordingly, a mismatch with a voice and a drop frame occur.
That is, when the delay occurs in the reproducing process of the motion image, generally, in order to solve the delay, a frame skip is conducted to omit the decoding process with respect to some frames. As a result, the drop frame occurs. Then, a reproduced motion image shows an awkward movement. Especially, in the Motion JPEG 2000 in that a high compression rate and a high quality of the image can be obtained, since a large amount of operations is required more than the image process of the Motion JPEG, the drop frame becomes remarkable.
In order to eliminate such these problems, the Japanese Laid-Open Patent Application No. 2001-309303 discloses a technology related to a real time picture recording and reproducing device using a digital motion image compressing and decompressing process in that a frame rate controlling part is included, an interpolating process is conducted when a compressing process cannot be conducted in time, and a frame dropping process is conducted when a decompressing process cannot be in time. In particular, the frame dropping process during the decompressing process is conducted preferentially with respect to frames for which the interpolating process is conducted during the compressing process.
However, according to the technology disclosed in the Japanese Laid-Open Patent Application No. 2001-309303 above-described, the interpolating process during the compressing process is substantially a thinning out process. As a result, a frame rate is deteriorated. Actually, a real time operation is maintained by deteriorating the frame rate by thinning out the frames. Accordingly, the motion image displayed at a display unit is an image which movement is not smooth.